The pond's shape matters: differential growth,physiological condition and survival of epibenthic Farfantepenaeus aztecus postlarvae

As a function of the water quality provided by square, circular and oval experimental ponds, the growth, survival and oxygen requirements in epibenthic postlarvae of Farfantepenaeus aztecus were analysed in relation to their routine metabolism and apparent heat increment. Temperature, oxygen concentration, pH and salinity were measured daily in two experimental ponds of each shape. The postlarvae oxygen consumption during two 24‐h cycles, their growth, physiological condition and survival and the productivity in the ponds were estimated. Low values of pH, oxygen concentration and phytobenthos productivity, and reduced postlarvae relative growth and survival were observed in the square ponds. We suggest that the latter results from a deficient water circulation related to the effect of the pond's shape on dissolved oxygen levels and, consequently, on growth and survival. The postlarvae routine metabolism, including feeding, varied between 1.91 and 2.25 mg O₂ h^?1 g^?1 wet weight, whereas the minimum oxygen concentration needed in the ponds is approximately 4.25 mg O₂ L^?1. These conditions were achieved in the oval ponds concurrent with higher survival and growth values, in which individuals distributed randomly, for which we suggest that oval‐shaped ponds could be the most adequate for the culture of this and other penaeid species.     

北方半湿润滨海地区海水养殖废水灌溉菊芋研究

2007年3~10月,在山东莱州海洋863中试基地,研究了海水养殖废水灌溉条件下,耐盐能源植物菊芋的盐胁迫响应以及对氮、磷的吸收利用机制。结果表明:海水养殖废水灌溉条件下,菊芋地上部生物量(茎、叶)随着灌溉水盐度(S)的增加明显下降,盐度为9.46 g/L的养殖废水处理生物量仅为淡水处理(CK2)的62.5%;地下部生物量(根、块茎)与盐度之间的关系符合一元二次方程曲线,且当盐度为3.83 g/L时,地下部生物量取得最大值(0.205 kg/株)。养殖废水处理菊芋地上部氮浓度明显低于淡水处理,地下部则各灌溉水处理间氮浓度没有明显差异;磷浓度地上部各灌溉水处理间没有明显差异,但地下部养殖废水灌溉处理明显高于淡水处理,表明海水养殖废水灌溉可以促进菊芋对磷的吸收,但氮利用受到显著影响。通过氮、磷通量计算,进一步证实了这一结果。     

Changes in epidemiological patterns of sea lice infestation on farmed Atlantic salmon, Salmo salar L., in Scotland between 1996 and 2006

Analyses of a unique database containing sea lice records over an 11 year period provide evidence of changing infestation patterns in Scotland. The data, collected from more than 50 commercial Atlantic salmon farms, indicate that both species of sea lice commonly found in Scotland, Lepeophtheirus salmonis and Caligus elongatus, have declined on farms over the past decade. Reductions for both species have been particularly marked since 2001 when more effective veterinary medicines became available. Treatment data were also available in the database and these show a growing trend towards the use of the in-feed medication emamectin benzoate (Slice), particularly in the first year of the salmon production cycle. However, this trend towards single product use has not been sustained in 2006, the latest year for which data are available. There is some evidence of region to region variation within Scotland with the Western Isles experiencing higher levels of infestation. However, compared to the levels observed between 1996 and 2000, all regions have benefited from reduced lice infestation, with the overall pattern showing a particular reduction in the second and third quarters of the second year of production.     

Mutualism between euryhaline tilapia Sarotherodon melanotheron heudelotii and Chlorella sp.—Implications for nano-algal production in warmwater phytoplankton-based recirculating systems

The West-African euryhaline tilapia, Sarotherodon melanotheron heudelotii shift from visually feeding on zooplankton when juveniles to mostly filter feeding on phytoplankton when adults. When reared using an appropriate ration in intensive aquaculture systems, S. m. heudelotii also consume algal-based detritus, and contribute to sediment mineralization, clean up their environment, and ultimately stimulate and sustain algal growth. We analysed such practical advantages for phytoplankton-based recirculating systems, using S. m. heudelotii and Chlorella sp. as biological material originating from the prototype of such a system operated in Senegal. We performed a 24-h factorial design experiment in 36 tubs, cross-classifying three levels of S. m. heudelotii (fishless control, unfed fish, and fed fish) with four levels of Chlorella initial density.Chlorella overall mean density increased significantly from fishless, to unfed fish, and fed fish treatments, and with Chlorella initial density. S. m. heudelotii did not alter nitrogen nor phosphorus concentrations, only affected by algal initial densities. Most ammonia excreted by fish was probably uptaken by Chlorella. Bacteria-mediated diurnal nitrification was possibly an alternative ammonium loss mechanism at highest oxygen concentrations. Algae were not limited by nitrogen or phosphorus but most likely by low dissolved organic carbon availability. Chlorella differential responses with fed vs. unfed Sarotherodon suggest that CO₂ supplied by heterotrophic S. m. heudelotii respiration played a key role. Observed Chlorella growth rates were similar to the highest rates obtained in algal mass cultures, enriched with CO₂, nitrate and phosphate, under artificial lighting.Our results suggest the existence of a Sarotherodon-Chlorella mutualism in our systems, where S. m. heudelotii provide CO₂, the major limiting factor of Chlorella growth, whereas Chlorella oxygenate and detoxify the water media from ammonia, promoting S. m. heudelotii production. This mutualism could be used to optimize photosynthetic suspended-growth aquaculture systems, particularly in the Tropics where light is abundant and temperature is continuously high.     

Dynamical analysis of net cage structures for marine aquaculture: Numerical simulation and model testing

A numerical model for analyzing dynamic properties of a net-cage system exposed in the open sea is proposed. The model is based on a lumped-mass method. In this model, the mooring lines are divided into linear elements and the net cage divided into several plane surface elements. The interconnected points or corners are called nodes or lumped-mass centers. The external force is calculated on each element and then equally distributed to its nodes. By adding the contributed forces from the neighboring elements, a system of motion equations for nodes is formed. The volume reduction coefficient of a net cage is estimated by the ratio of minimum volume of net cage during fluid and structure interaction to the original volume. In general, the numerical results are in good agreements with the experimental data. However, the results also show that if the Reynolds number is lower than the suggested range of 1400–1800, the numerical model may underestimate the environmental forces on a net-cage system.     

河蟹青虾混养池塘循环水净化效能的初步分析

在河蟹青虾混养池塘构建封闭式循环水养殖系统,并对其净化效果和养殖效益进行了初步研究。结果表明：该系统对水体TN、TP、NH4＋-N和CODMn的平均净化效率分别为27.33%、56.14%、43.91%和39.59%。经湿地净化后的水质能够达到GB3838-2002地表水Ⅲ类排放标准,平均纯收益达53769元/hm2。     

喹诺酮类药物在水产养殖中的应用研究概况

以抗菌素为主的药物防治已成为水产养殖业病害治疗的重要措施,其中喹诺酮类药物在水产上的应用尤为广泛。由于水产用药仍存在盲目性,故对药物的应用研究具有重要的意义。文章综述了近年来喹诺酮类药物的研究现状及其在水产方面的应用和药物代谢研究概况,并对其发展前景进行了展望。     

Exploring the efficacy of vaccine techniques in juvenile sablefish,Anoplopoma fimbria

Wild sablefish, Anoplopoma fimbria, are a valuable commercial species whose populations are declining. Fortunately, sablefish are excellent species for commercial aquaculture. Sablefish raised under high‐density conditions in the marine environment require the use of efficacious vaccines to control disease. Sablefish impacted by disease in net pens may have poor flesh quality and high mortality during grow‐out. As a result, disease can cause financial hardship for sablefish aquaculture operators. The efficacy of a multivalent vaccine preparation for sablefish, administered either by intraperitoneal (i.p.) injection or by immersion, against atypical and typical Aeromonas salmonicida, the causative agents of atypical and typical furunculosis, respectively, was examined. A. salmonicida can affect sablefish at any age and size. Consequently, an efficacious vaccine that can be appropriately and optimally administered to all life stages is desirable. Sablefish vaccinated by immersion at ~1.5 or ~4.5 g with a whole‐cell multivalent vaccine were not protected against either typical or atypical A. salmonicida. Factors that may have contributed to the ineffectiveness of the immersion vaccine are discussed. By contrast, the relative per cent survival (RPS) or potency of the whole‐cell multivalent vaccine injected i.p. in juvenile sablefish at ~50 g against typical and atypical A. salmonicida was 94.3% and 81.7% respectively. The high RPS values indicated that the vaccine successfully initiated an immune response in sablefish upon a second encounter with the pathogen.     

The dynamics of bacterial community in a polyculture aquaculture system of Penaeus chinensis,Rhopilema esculenta and Sinonovacula constricta

Polyculture with Chinese shrimp Penaeus chinensis, jellyfish Rhopilema esculenta and razor clam Sinonovacula constricta (S.J.R) is a common aquaculture system in Dandong, China. Investigation on the composition and function of microbial communities and their relationship with environmental factors in aquaculture systems have crucial implications. Therefore, the sequencing of 16S rRNA gene was applied to profile the bacterial community composition of water and sediment in S.J.R polyculture system in the present study. Proteobacteria was the dominant phylum in S.J.R polyculture ponds following with Actinobacteria and Bacteroidetes in water; in contrast, more diverse phyla were detected in sediments. Water temperature, pH and dissolved oxygen were determined the bacterial community composition in the S.J.R polyculture systems. Specially, Planktomarina, PS1 clade, Candidatus Aquiluna and Fibrobacteres, which can resist the phytoplankton blooms or degrade the cellulose, were more abundant in water at the early stage of cultivation in the S.J.R polyculture system. Moreover, the functions of bacterial communities in water were mainly associated with cell communication mediated, while the functions related to basal metabolism were enriched in sediments. The findings of this study allowed us to better understand the bacterial community in the S.J.R polyculture system and accumulated data for the improvement of cultural management.     

Effects of dietary phosphorus level on non-faecal phosphorus excretion from yellowtail (Seriola quinqueradiata Temminck & Schlegel) fed purified and practical diets

Non-faecal phosphorus (P) was determined for large yellowtail to estimate a minimum available P requirement (Experiment  1) and to justify inorganic P supplementation in a fish meal-based diet (Experiment 2). In Experiment 1, purified diets with incremental P concentrations were fed to yellowtail (mean weight 917 g) at a feeding rate of 1.5% of body weight. The peaks of non-faecal P excretion appeared 5–6 h after feeding in fish fed more than 4.5 g available P kg⁻¹ dry diet. Broken-line analysis indicated that the minimum available P requirement was 4.4 g kg⁻¹ dry diet. In Experiment 2, a purified diet (PR) containing 6.5 g available P kg⁻¹ and a fish meal-based diet with (F1) and without (F0) additional phosphorus were fed to yellowtail (mean weight 1.1 kg) at 1.5% (PR) and 2% (F0 and F1) feeding rates respectively. There was no significant difference in P excretion between fish fed the F0 (5.5 g soluble P kg⁻¹ dry diet) and the PR diet. However, significantly higher (34.5%) amounts of non-faecal P excretions (7.4 g soluble P kg⁻¹ dry diet) were found in fish fed F1 compared with the F0 diet. This suggested that there was an excess of dietary P in the F1 diet and that supplementation is not needed in fish meal-based diets for large yellowtail.